Muffler body and method of manufacture



Aug. 29, 1967 R. E. PARKINSON MUFFLER BODY AND METHOD OF MANUFACTURE Filed June 5, 1965 IME ENTOW.

WOHEF? T 1 fimajw zab Afforney United States Patent 3,337,939 MUFFLER BODY AND METHOD OF MANUFACTURE Robert E. Parkinson, Monroeville, Pa., assignor to United States Steel Corporation, a corporation of Delaware Filed June 3, 1963, Ser. No. 284,913 3 Claims. (Cl. 29-157) This invention relates to mufllers for silencing the exhaust of internal-combustion engines. In particular, it pertains to a mufiier having an improved body or outer shell, and to an improved method of making it.

The outer shell of the muflier is subject to a variety of atmospheric conditions and substances causing rapid deterioration and eventual complete failure thereof. On the inside, strongly oxidizing exhaust gases at high temperatures create rust problems, and corrosion is formed by deposits of carbonaceous matter left by the exhaust gases. On the exterior, the muffler body is attacked by moisture sometimes holding salt in solution, and other deposits encountered under normal operation conditions.

The mufiler body, to be satisfactory, must have sounddeadening characteristics built into it. One method of imparting such characteristics is to construct the body from two sheet-s of metal, separated by a thin, nonmetallic layer of sound-deadening material, such as asbestos paper. It is the present practice to form and lock seam each sheet of metal separately to produce two cylinders, each having the shape of the muffler body. The non-metallic sound-deading material is wrapped around the outer surface of one of these cylinders, and the other cylinder, with one end left open, is slid over this sounddeadening material. The remaining end is then lock seamed onto the outer cylinder to produce the finished product. Although this multiple-layer muffler body possesses good sound-deadening characteristics, its manufacture requires a complicated and expensive method of assembly.

Much effort has been directed toward the development of muffler bodies with longer lives which will retain a satisfactory sound-deadening property and yet be competitive from a cost standpoint. Ceramic coated mufllers are now being used commercially, but they have been found too noisy and have not given consistently longer service than plain steel mufflers, because of occasional uncoated spots and cracks that occur in the ceramic coating. Mufliers have also been made entirely of stainlesssteel, but they have been considered too expensive for the resulting gain in service life.

It is therefore an object of my invention to provide an inexpensive mufiier body having an improved service life comparable to that of more expensive muffler bodies.

It is a further object of my invention to provide a multiple-layer mufiler body which has a superior sounddeadening character and may be assembled by a low-cost method similar to that used in the construction of singlelayer muffler bodies.

The attainment of these and other objects by my invention will appear more readily from the following detailed description thereof and the attached drawing, the single figure of which is a perspective view of a muflier body in partial section.

Referring to the drawing, a mufiier body B is connected to an exhaust-inlet pipe E at one end, and to exhaustoutlet pipe X at the opposite end. The muifier body B is composed of a center sheet 1 rolled into a cylinder, and two end sheets 2 lock seamed to the ends of the cylinder. The center sheet 1 and the end sheets 2 are ach composed of three layers. Two metallic layers 11 and 12 are separated by a third non-metallic, sound-deadening layer 13.

3,337,939 Patented Aug. 29, 1967 The outer metallic layer 11 is a sheet of carbon steel, which is preferably either galvanized or aluminum coated for increased resistance to moisture and salt deposits. This sheet 11 may be of any thickness suflicient to provide the muffler body with the required strength and rigidity. In most applications, sheet thicknesses ranging between .027 and .040 inch are suitable.

The inner metallic layer 12 is a sheet of stainless steel for resistance to internal corrosion and oxidation. To make the mufiier body less expensive, it is preferred that this sheet be as thin as possible without impairing its ability to withstand the hot exhaust gases and corrosive particles deposited in the mufiler. Stainless-steel sheets having thicknesses ranging between .005 and .010 inch should be suitable under most conditions.

An adhesive material is used for the intermediate sound-deadening layer 13. Initially, this material serves to bond together the metal sheets 11 and 12 while they are being bent to form the muffler body. Thus, a requirement of the adhesive is that it hold a metal-to-metal bond and not crumble during the shaping of the mufiler body. The adhesive must also be non-volatile at muffler operating temperatures, and in addition must be either of a type which carbonizes to form a sound-deadening char when heated, or a type which possesses the required sounddeadening properties without heating. Epoxy adhesives and rubber-phenolic adhesives are satisfactory types which form sound-deadening chars when heated.

In the production of the muffler body B, the metal sheets 11 and 12 are first bonded together with the adhesive layer 13 to form flat composite sheets. These composite sheets are then rolled and lock seamed together in the conventional manner used in assembling singlelayer mufller bodies. After the mufller body has been assembled, it is placed in an oven and heated at a temperature sufficient to carbonize the adhesive, thus transforming the adhesive into a non-continuous char with sound-deadening voids. This char has been found to be capable of holding the inner metal sheet 12 separated from and firmly supported within the outer metal sheet 11. In addition, the porous char layer gives the muffler body an excellent sound-deadening character.

The heating and carbonizing of the adhesive as a step in the manufacture of the mufiler may be eliminated if, during its expected use, the mufiier will be heated to temperatures sufiicient to carbonize the adhesive. Also, there is no need to heat the mufiler if the adhesive used possesses satisfactory sound-deadening properties without heating.

As an example of the practice of my invention, a sheet of aluminum coated steel having a thickness of about .048 inch was bonded to a stainless-steel sheet having a thickness of about .010 inch. The adhesive used was a .0005 inch layer of compound EC1386, an epoxy resin produced by the Minnesota Mining and Manufacturing Company. After bonding, the resulting composite sheet was rolled into a cylinder, and similarly constructed end sheets were attached to this cylinder by lock seaming. The assembled mufiler body was placed in an oven preheated to a temperature of 400 F. The temperature of the oven was then raised to 1100 F., and at the end of thirty minutes, the muffler body was removed from the oven. A thin, charred residue of adhesive remained between the stainless-steel and aluminum coated steel layers, and the inner stainless-steel layer remained firmly in place. The mufiler body was found to be acoustically dead.

Thus, by forming a mufiler body out of a composite sheet comprising two layers of corrosion resistant metals bonded together by a layer of adhesive, and then heating this assembled body to carbonize the adhesive, the resultthe inner metallic layer a relatively thin sheet of stainlesssteel, which is highly resistant to high temperature oxidation and corrosion, and by using for the outer layer a thicker sheet of lower cost aluminum coated or galvanized steel to effectively resist the external corroding elements, a muffier body with a greatly increased service life has been produced at only a relatively small increase in cost.

While one embodiment and practice of my invention have been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim: I

1. A method of manufacturing a muffier body having a superior sound-deadening character, comprising bonding two sheets of metal together with a carbonizable adhesive to form a composite sheet, fabricating from said composite sheet a mufiler body comprising a side wall and ends, and heating said mufiler body to a temperature sufiicient to carbonize said adhesive, thereby imparting to said adhesive a sound-deadening character.

2. A method of manufacturing a mufller body, comprising bonding with a carbonizable adhesive a sheet of carbon steel to a sheet of stainless-steel to produce a composite sheet, forming and joining said composite sheet with ends of the same material to produce a muffler body with a stainless-steel interior, and heating said mufiier body at a temperature sufficient to carbonize said adhesive.

3. The method of claim 2 wherein said mufller body is heated in an oven for a period of about thirty minutes, while said oven is maintained at a temperature of between 400 F. and 1100 F.

References Cited UNITED STATES PATENTS 744,495 11/ 1903 Corse 181-62 929,656 8/1909 Coles 181-62 X 2,187,431 1/ 1940 Powell 29157 2,367,753 1/1945 Buck 29-157 2,598,756 6/1952 Brightly et a1. 2,624,418 1/1953 Bourne 18161 X 2,653,889 9/1953 Hager et al. 2,761,525 9/1956 Moss 18162 2,824,619 2/1958 Bremer et a1. 3,158,222 11/1964 Richmond 18161 X 3,262,189 7/1966 Nordquest et a1. 29--458 X OTHER REFERENCES Sears, Roebuck and Company Catalog For Spring and Summer of 1959, p. 1118.

JOHN F. CAMPBELL, Primary Examiner.

D. SMILAN, Examiner.

I. L. CLINE, R. S. WARD, Assistant Examiners. 

1. A METHOD OF MANUFACTURING A MUFFLER BODY HAVING A SUPERIOR SOUND-DEADENING CHARACTER, COMPRISING BONDING TWO SHEETS OF METAL TOGETHER WITH A CARBONIZABLE ADHESIVE TO FORM A COMPOSITE SHEET, FABRICATING FROM SAID COMPOSITE SHEET A MUFFLER BODY COMPRISING A SIDE WALL AND ENDS, AND HEATING SAID MUFFLER BODY TO A TEMPERATURE SUFFICIENT TO CARBONIZE SAID ADHESIVE, THEREBY IMPARING TO SAID ADHESIVE A SOUND-DEADENING CHARACTER. 